/* 
连接数据库
*/
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/hf_qf', {
  useNewUrlParser: true,
  useUnifiedTopology: true
});
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  // we're connected!
  console.log('mongodb连接上了');
});